Unanswered question

This question is related to my earlier question about combining the response time of redirection. While the suggested answer will work in that case, I am looking for a general answer.

How do I capture the response time of an element, store it in a variable and then do some calculations with it? For example, can I create a validation rule that says the test fails if the sum of the response times of several non-consecutive pages exceeds a certain time limit? Thanks.